Describing MotionDescribing Motion

Ch 2 sect 1Ch 2 sect 1

ChallengeChallenge

Can you describe motion without using the Can you describe motion without using the word move?word move?

MotionMotion

Motion occurs when an object changes its Motion occurs when an object changes its position position When something goes from one spot to When something goes from one spot to

another then motion has occurredanother then motion has occurred

If you are sitting completely still with no If you are sitting completely still with no movement, are you in motion?movement, are you in motion?

Relative MotionRelative Motion

The correct answer is yes and no because of The correct answer is yes and no because of relative motionrelative motionRelative motion depends on what we are Relative motion depends on what we are comparing motion tocomparing motion to– Sitting completely still you are not in motion Sitting completely still you are not in motion

compared to the room you are incompared to the room you are in– Even if you are sitting completely still you Even if you are sitting completely still you

are in motion compared to the sun b/c you are in motion compared to the sun b/c you are on the earth and the earth is moving are on the earth and the earth is moving around the sunaround the sun

Relative Motion, Physics, Relative Motion, Physics, and Earth Scienceand Earth Science

Science has shown that the surface of the Science has shown that the surface of the earth is broken into a bunch of different earth is broken into a bunch of different sectionssections– These sections are called plate tectonicsThese sections are called plate tectonics

Plate tectonics are in constant motion, Plate tectonics are in constant motion, therefore you are always in motion relative therefore you are always in motion relative to other continents.to other continents.

What evidence supports plate tectonicsWhat evidence supports plate tectonics

Describing MotionDescribing Motion

• There are two words which we will There are two words which we will begin describing motion with.begin describing motion with.1. Distance - Distance refers to how far 1. Distance - Distance refers to how far

something has movedsomething has moved•Distance must have a unit and a number Distance must have a unit and a number

attached to itattached to it

Describing Motion (continued)Describing Motion (continued)

2. Displacement - Displacement 2. Displacement - Displacement describes how far as well as which describes how far as well as which direction the object is from its starting direction the object is from its starting pointpoint

Rate and SpeedRate and Speed

Rate-Change over timeRate-Change over time Ex.-rate of growth may be 2 cm’s per Ex.-rate of growth may be 2 cm’s per

yearyear Speed-Distance traveled in a given Speed-Distance traveled in a given

amount of time amount of time Speed is measured in meters/secSpeed is measured in meters/sec To calculate speed we use the equation To calculate speed we use the equation

Speed = Speed = DistanceDistance or S = or S = DD

TimeTime T T

Types of SpeedTypes of Speed

There are two different types of speedThere are two different types of speed

1.1. Instantaneous Speed-Speed at any Instantaneous Speed-Speed at any given point and timegiven point and time

Ex.-Looking at the speedometer in your car, Ex.-Looking at the speedometer in your car, it tells how fast you are traveling nowit tells how fast you are traveling now

Types of Speed (cont)Types of Speed (cont)

2. Average Speed-Distance covered over a 2. Average Speed-Distance covered over a set time period. set time period. Takes into account the changes in speedTakes into account the changes in speed This is where we use our equation for speedThis is where we use our equation for speed

Speed = Speed = DistanceDistance

TimeTime

Graphing MotionGraphing Motion

There are two basic graphs that can be There are two basic graphs that can be used when showing motionused when showing motion

1.1. Distance-time graph: A distance-time graph Distance-time graph: A distance-time graph shows how far an object has traveled as well shows how far an object has traveled as well as how long it tookas how long it took

2.2. Displacement-time graph: A displacement Displacement-time graph: A displacement time graph shows how far an object is away time graph shows how far an object is away from its starting pointfrom its starting point

Graphing Motion (continued)Graphing Motion (continued)

When graphing motionWhen graphing motion Time is always on the x axisTime is always on the x axis Distance or Displacement are always on the Y Distance or Displacement are always on the Y

axisaxis You can never have a vertical lineYou can never have a vertical line

• Why???Why??? It is possible to have a horizontal lineIt is possible to have a horizontal line

• Why??Why??

VelocityVelocity

Velocity describes the speed and direction Velocity describes the speed and direction of an objectof an object If you have escalators that are next to each If you have escalators that are next to each

other and running the exact same speed, do other and running the exact same speed, do they have the same velocity?they have the same velocity?• Yes or No and why-Yes or No and why-

If you have have a car that is traveling at 20 If you have have a car that is traveling at 20 meters per second (constantly) in a circle meters per second (constantly) in a circle does that car have the same velocity?does that car have the same velocity?• Yes or No and why-Yes or No and why-